SEATTLE — Traffic was piling up going from West Seattle to Interstate 5 — and that meant Rich Feldman had to drive a few feet and stop, over and over, all the way up the access ramp.

As they looked out at the line of cars ahead of their plug-in Toyota Prius, Feldman and the business executive sitting beside him, John Clark, couldn't have been happier.

"This is the perfect kind of traffic. We love traffic like this," Clark enthused. A couple of minutes later, Clark peeked at his laptop computer and gave Feldman the good news: "You're at 159 on this trip," he said. That's 159 miles per gallon.

Feldman, a senior policy adviser in the Seattle mayor's office, and Clark, the president and chief executive officer of Seattle-based V2Green, were giving an on-the-road demonstration of how plug-in electric vehicles will change the way people think about driving — and about using electricity.

The converted Toyota Prius that Feldman was driving is the first of 14 vehicles that will be used by Seattle's municipal utility and other regional agencies to gather data on plug-in driving patterns, as part of a yearlong experiment monitored by the U.S. Department of Energy's Idaho National Laboratory.

V2Green — which was acquired just this week by another clean-energy company, Virginia-based GridPoint — is providing hardware and software enhancements that will let researchers monitor every move the cars make. V2Green's system sends telemetry from the car continuously via a cellular phone link to a remote computer. The readings are analyzed on a remote computer, and then posted on a password-protected Web site.

The read-outs on the car's speed, mileage, fuel economy and location are far more detailed than the numbers displayed on the Prius' dashboard display. What's more, they can be checked remotely on a wireless laptop (like Clark's) or back at the Idaho Falls lab, usually in real time. The experiment serves as a minute-by-minute reality check for the current hype over plug-in hybrids.

"It's looking at the vehicles first, and asking if this is a feasible way, economically and technologically, to move people," said Jim Francfort, the project's lead researcher.

The hot new thing
Plug-in hybrid electric vehicles, or PHEVs, are the hot new thing in automotive technology: Some cars, such as Seattle City Light's motor-pool Prius, are already being converted into PHEVs. Toyota as well as GM, Chrysler and other automakers are talking about rolling out showroom-ready PHEVs in the 2010 time frame.

At current energy rates, the per-mile cost of running an electric vehicle is about a quarter the equivalent cost for gasoline. That doesn't consider the higher up-front cost of electric vehicles or the back-end cost of battery replacement. There may be other factors that affect PHEV performance as well, and that's the whole point of the pilot projects being conducted in Seattle and elsewhere.

The Energy Department is working with utilities across the country to measure the actual performance of present-day PHEVs, and figure out how their rise could affect electrical usage patterns in the years ahead. The studies could lead to "smart charging" technologies, with incentives for consumers who charge up their cars during off-peak hours.

Previous studies have found that no additional power plants would be required to power the millions of PHEVs expected to be on U.S. roads in 2030 — that is, if off-peak smart charging is available. But if every PHEV driver decided to charge up at 5 p.m., researchers said 160 additional large plants would have to be built in the next 20 years to handle the load.

Invisible to consumers
Colorado-based Xcel Energy has been studying smart-charging techniques over the past year as part of its SmartGridCity pilot project. Consumers can plug in their specially equipped Ford Escape PHEVs anytime they want to. However, the actual charging is scheduled by the utility, based on the car's driving history. Xcel switches on the flow of power into the car's batteries via a cell-phone link.

The next phase of the experiment will test vehicle-to-grid electrical flow. The "V2G" scheme would enable a utility to borrow power from a plugged-in car's battery to cope with peak electrical loads (with the car owner's advance permission, of course). Once the peak has passed, the borrowed power would be put back in the battery. Like smart charging, V2G would provide a payoff to the consumer in the form of a rate break or a rebate for utility charges.

Sandy K. Simon, Xcel's director of utility innovation and SmartGrid strategy, said the smart-charging experiment has worked pretty much as expected so far. The system is essentially invisible to consumers.

"We haven't had any issues with the battery being drawn down when they needed it," she said.

When it comes to plug-ins, the most noticeable adjustment takes place behind the wheel rather than under the hood. "What we did see was huge behavioral changes in how people drive," Simon said.

PHEVolution at work
The behavioral changes sparked by plug-in vehicles were on full display during last week's test drive with Feldman. Every move was as gradual as possible — including his smooth acceleration to blend into freeway traffic, even when a cement truck was coming up close behind.

Studies have shown that less aggressive driving is one of the biggest factor behind better fuel economy — not only for PHEVs and other hybrids, but for traditional gasoline-powered vehicles as well. Punching on the accelerator uses up more spurts of gasoline than gently getting up to your cruising speed.

The big difference for hybrids — and particularly for the V2Green-equipped PHEVs — is that the miles-per-gallon readings are continuously on display. Even if you're not reading the numbers, you know that someone else is. For example, Francfort could check a GPS display on his office computer in Idaho to check on Feldman's mileage performance in Seattle, and even see which lane on I-5 he was driving in.

"How am I doing?" Feldman asked Francfort over a speaker phone. "Do I have a lead foot?"

"No," Francfort answered. "I think 106 miles per gallon is not so bad."

Feldman was getting that kind of mileage because much of the power was coming from the Hymotion lithium-ion battery that was installed in the Prius' trunk, at a conversion cost of roughly $10,000. The extra electrical boost means the car's gasoline engine comes on less frequently, at least until the batteries run down.

Sweet spot for electric power
Feldman, who drives a standard-issue Prius when he's off-duty, said he can notice a difference between his own car and the city-owned PHEV when he drives up an incline. The PHEV could take an uphill access ramp without a single gasoline-fired boost. "In my car, I cannot do this," Feldman said.

PHEVs don't give you much of a fuel economy advantage for a trip around the block, because the gasoline engine has to be fired up at first to warm up the catalytic converter. And the all-electric advantage fades away on an extended trip when the batteries run out. But for a medium-length trip, a PHEV is just right.

For example, on the 18.3-mile trip out from West Seattle across Lake Washington to Redmond, Feldman hit a fuel economy mark of 108 miles per gallon by using just 0.17 gallon of gas. By that time, however, the batteries were drained to 11 percent of capacity. The 13.3-mile trip back to downtown Seattle used up 0.22 gallons of gas, resulting in a 60-mpg performance.

When V2Green's software added up all of that day's trips, the distance driven came to a little more than 40 miles. That used up half a gallon of gas, which translates to 81 miles per gallon. Total cost, including the price tag for 3.98 kilowatts of electricity: $2.91.

That's the kind of real-world data that the Idaho National Laboratory hopes to pile up over the next year or so. As a result, carmakers may find it worth their while to build additional intelligence into future electric vehicles. Utilities just might enlist smart-charging technology and incentive programs to accommodate a new wave of drivers. And drivers could be using new gizmos to save money at the gas pump — and on their electric bill.

It might even be fun.

"This is the next level up," Feldman said, pointing to Clark's laptop. "People are really going to get into computer-game mode in terms of seeing what they can do."